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Re: Howdy (Reply to this comment)
by oldzip
I replied privately to this comment and didn't hear anything back so am making my comments public:
I appreciate the time you took to look over my review.
The way I'm thinking I still think I'm correct. Let's suppose we're still using core memory. Core memory has a latency of 1. If it's correct to use that term. On every machine cycle you can read a memory location and restore the contents; as by reading it you erase it. If you're doing a write the first half cycle instead of reading you just twiddle thumbs and during the second half cycle instead of doing a restore you insert the new data. You're done writing. On the next machine cycle you're free to access a memory location, anywhere in memory with no delay.
Core memory unlike RAM was truly Random Access Memory. You can write or read on every machine cycle anywhere in the entire memory on the machine.
Ram has all these delays. It doesn't truly run at the bus speed. When you have CL2 memory you skip a machine cycle. With CL3 memory you skip 2 cycles for each access, read or write. When you change rows the RAS delay will cause a delay of at least 3 more cycles. If you have CL3 memory with say a RAS delay of 4, which is very normal memory, your computer is running at 57 MHz with a 400MHz bus. When I say the CPU speed of say 3.6GHz isn't relevant, I'm being gracious. With CL2 memory and a RAS delay of 3 your computer will run at 80MHz. That a 40% improvement. That's significant.
Core memory was said to be non-volatile, even shutting off the power didn't effect the contents. The only thing that did was reading a location. RAM memory slowly degrades over time. A very short period of time. All these delays are, in part, to allow time to refresh the contents. I suspect that another reason is to allow the salesmen to quote better looking numbers to those unaware of the real background story.
When your program is running you access alternatively instructions and data. We used to call them operands. For each instruction you have a an instruction call and a data operand call.
What's significant here is that when you execute an instruction you need to get the data for that instruction, also from memory. However the data is never going to be near the address of the instruction and certainly not on the same row. If you're lucky to be executing an instruction which executes in one instruction cycle followed by a second similar instruction, the computer will execute these two instructions at 57 MHz.
The difference between the 66MHz memory, of the past, and 400MHz memory is the comparison between two slow memories. I'd rather have the 400 than the 66 but I'm not overwhelmed by either.
After I published the review I realized that in my discussion I failed to mention that the DDR-II memory doesn't have a dual channel option. When I stated that the reviewed memory was the best on the market, I was stating an honest opinion of the market. There is ECC memory and buffered memory, but for the memory we buy for our PC's that's the best out there. I did say that: I may not have shopped too well. But I spent a lot of time looking.
What I tried to do when I built this computer was to spend my money wisely, ignoring the Bus Speed (BS). I looked at price points on CPU's, considered the heat (read fan noise) and bought the best memory I could find. I think I got the difference between salesman's memory and the best memory free with the money I saved on useless CPU speed. To tell you the truth I would have hoped that the best I could find was another brand. There are better rated memory companies, but I went with what was in my opinion the best.
What I found while shopping was that after you reached PC3200 memory there wasn't any more CL2 memory at a faster Bus Speed. I'm sure that someone will find an example, but I didn't. If you find an example let us all know.
When I mentioned the DDR II memory I neglected to mention that this memory doesn't have the capability of running dual channel making the new memory an even worse choice. I have recently seen a reference to dual channel DDR II memory so maybe that's (hopefully) been upgraded.
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Dec 03 '05
9:33 pm PST
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Howdy (Reply to this comment)
by jwhitakr
I rated your review as Helpful because, while you did give your experience with the RAM and how well it has performed for you, you have some mis-information listed in your review:
"DDRII memory runs at 533MHz with a Cas Latency of 4. That means an ultimate speed of 133 MHz."
There is no direct relationship between the clock speed and the CAS latency. To state that DDR2 memory running at 533MHz with CL4 timings is the same as memory running an "ultimate speed of 133 MHz" is not correct. (I can only assume you mean clock cycle of 133 MHz).
If you do update your review, pls feel free to email me and I will re-rate.
- Justin
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Nov 18 '05
7:15 am PST
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